Fix flickering on progress bar width update

Issue visible on lastest version of Chrome Browser (if you update progress bar width from 100% to 0%) -> flickering appears

Fixed with addition of .backface-visibility(hidden) mixins
update docs
Redo the getting started section to mention BootstrapCDN
Back to two grid classes, .col and .col-lg-*
Fix navbar on phone/tablet devices after navbar overhaul
Merge pull request #7713 from burnsra/3.0.0-wip-navs-overhaul

Fix navbar on phone/tablet devices after navbar overhaul
derp on navbar toggle and docs positions
Merge branch '3.0.0-wip' of github.com:twitter/bootstrap into 3.0.0-wip
Fix navbar-toggle after commit bbee78b30b40ff0b1473a06ea7ecf5a42d51b614

The following commit introduced an issue with the navbar toggle placement:
https://github.com/twitter/bootstrap/commit/bbee78b30b40ff0b1473a06ea7ecf5a42d51b614
Merge pull request #7716 from burnsra/3.0.0-wip-navbar

Fix navbar-toggle after commit bbee78b30b40ff0b1473a06ea7ecf5a42d51b614
Merge pull request #7704 from twitter/bs3_moar_grid_changes

BS3: Overhaul grid system once more
Cleanup breadcrumb divider last item

Modify to hide both padding and leading/trailing whitespace
Thanks to https://github.com/holic for suggestion
Update examples after grid changes
Merge pull request #7719 from burnsra/3.0.0-wip-grid-examples

Update examples after grid changes
Merge pull request #7718 from burnsra/3.0.0-wip-breadcrumbs

Cleanup breadcrumb divider last item
single colon pseudo element for ie8
Merge branch '3.0.0-wip' of github.com:twitter/bootstrap into 3.0.0-wip
nuke line numbers
Fixes #7744: update grid mixin to use latest grid styles
no units on 0 values